Vol 51, No 8 (2025)

A series of substituted o-iminobenzoquinones (6-((2,6-di-iso-propylphenyl)imino)-2,4-bis(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L¹), 4-(tert-butyl)-6-((2,6-di-iso-propylphenyl)imino)-3-methoxycyclohexa-2,4-dien-1-one (L²), and 6-((2,6-di-iso-propylphenyl)imino)-3-methoxy-4-(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L³)) were used to synthesize indium(III) iodide complexes containing the redox-active ligand in its neutral form. The o-iminobenzoquinone L¹ was synthesized for the first time. It was found that the structure of the obtained complexes depends on the degree of steric shielding of the carbonyl oxygen atom in the initial o-iminobenzoquinone. The sterically hindered ligand L¹ forms a 1:1 adduct with InI₃ (complex (L¹)InI₃ (I)). The absence of a substituent at the 2-position of the o-iminobenzoquinone ring promotes the formation of bis-ligand ionic derivatives {[(L²)₂InI₂]InI₄} (II) and {[(L³)₂InI₂]InI₄} (III). The molecular structures of L¹ and the complexes I·0.5toluene, II·toluene·0.5hexane were determined by X-ray diffraction analysis (CCDC deposition numbers: 2440874 (L¹), 2440875 (I·0.5toluene), 2440876 (II·toluene·0.5hexane)). The optical and electrochemical properties of the initial o-iminobenzoquinones and their corresponding indium(III) complexes were investigated. It was shown that complexation significantly enhances the oxidative properties of L¹, L², and L³.

A new N-donor ligand, methyl 4-(1-methyl-1H-perimidin-2-yl)nicotinate, and the corresponding octahedral cationic iridium(III) complex (1) were designed and synthesized. 1-Benzyl-2-phenyl[2,3]naphthimidazole was used as a cyclometalated ligand; PF₆^– served as a counterion. Compound 1 was characterized by ¹H, ¹³C, ¹⁹F, ³¹P, ¹H,¹H-COSY, ¹H,¹H-NOESY NMR, high-resolution mass spectrometry and X-ray diffraction. As a result of the combination of ligands containing a large conjugated system around the metal ion, the target complex exhibits light absorption up to 700 nm (ε ~ 1000 M^–1cm^–1), translating in its deep color. Complex 1 demonstrates reversible electrochemical behavior at positive potentials with E_1/2 = 0.58 V vs. E_Fc+/_Fc. In terms of the key characteristics, the resulting compound surpasses most iridium analogs, and therefore appears promising for further testing in photovoltaic devices.

The reaction of tetralone azine with methyllithium in tetrahydrofuran results in the release of 1 mol of CH₄ and the formation of the lithium salt of enamine I, which crystallizes as a dimer in which the lithium atoms are bridges between the sp³- and sp²-nitrogen atoms of the two ligands and form a six-membered LiNNLiNN metallacycle (CCDC No. 2426300). Analysis of the electron density topology using the non-covalent interaction index and the source function allowed us to determine that each lithium atom in complex I interacts with the NNCC fragment of the ligand. The study of the charge distribution in the ligand anion demonstrated that the C(2) position is the most favorable for directing the attack of various electrophilic substrates. The DFT method showed that the process of phosphorylation of the deprotonated azine tetralone PCl3 is thermodynamically more favorable by 12.6 kcal/mol than the product of phosphorylation at the nitrogen atom.